Integral forming or molding for producing resin containers with a label has conventionally been carried out by inserting a label or a blank in a mold beforehand and then molding or forming a container by injection molding, blow molding, differential pressure forming, foam molding, etc. Labels to be used include gravure printed resin films, multi-color offset printed synthetic paper [cf. JP-B-46-40794, JP-B-54-31030 (the term "JP-B" as used herein means an "examined published Japanese patent application"), and British Patent No. 1090059], and gravure printed aluminum foil having a polyethylene layer on the back side thereof.
When a label-decorated resin container is produced by fusing a label, inclusive of a blank, with a molten resin at a high pressure as in injection molding (e.g., 100 to 1000 kg/cm.sup.2), the resulting molded article has a satisfactory appearance. However, in the case of molding at a low pressure as in differential pressure forming (e.g., 2 to 7 kg/cm.sup.2) or blow molding (e.g., 1 to 10 kg/cm.sup.2), escaping of air between a blank and a molten container is insufficient only to provide containers having poor appearance due to trapped air-pockets called blisters.
To settle the above-described problem, the applicant previously proposed to use a label, inclusive of a blank, having an embossed finish on the back surface thereof so that the air between the label and a container may easily escape to thereby prevent blistering as disclosed in Japanese Utility Model Application No. 63-1775 (corresponding to unexamined published Japanese Utility Model Application No. 1-105960). This label for resin formed containers comprises a printed thermoplastic resin film having provided on its back side a heat-sealable resin layer having a melting point lower than that of the thermoplastic resin film, the heat-sealable resin layer having an embossed pattern of 5 to 25 lines per inch.
On the other hand, it has also been proposed to orient a multi-layer film by stretching to provide a thinskinned label having nerve as described in the working examples of the above cited application.
Where synthetic paper is embossed after orientation, an emboss is easily formed to a large depth (h) and, as a result, the nerve having been increased by orientation is more or less reduced. Unless the label has nerve to some extent, errors occur in fixing a label to the inner wall of a mold by means of a sucking pad of an automatic label feeder.